Drawtwisting process



March 20, 1962 v. E. GONSALVES DRAWTWISTING PROCESS Filed Jan. 13, 1958 INVENTOR. VICTOR EMANUEL GONSALVES ATO Stats fibre 3,025,660 DRAWTWISTHNG PRfiCESS Victor Emanuel Gonsalves, Arnhem, Netherlands, as-

signor to American Erika Qorporation, Erika, N.C., a

corporation of Delaware Filed Jan. 13, 1958, Ser. No. 708,689 Claims priority, application Netherlands Jan. 24, 1957 2 Claims. (Cl. 57-157) The present invention relates in general to the draw twisting of yarn formed from linear polycondensation products and more particularly to a drawtwisting process resulting in a substantial elimination of undesirable barr usually found in fabrics woven from drawn and twisted polyamide yarns.

In the commercial production of drawn and twisted yarn formed from linear polycondensation products, especially polyarnides, the yarn usually is drawn, after which it may be subjected to a heat treatment, if desired, then twisted and wound on a ring twisting machine, all in one continuous operation. When yarn produced in this man ner is woven into fabric, it has been found that a distinct barr eifect results. For the purpose of this application barr may be defined as the regular occurrence or the occurrence at regular intervals of stripes or streaks in the woven fabric, resulting in an unattractive appearance which is generally considered to be a defect in the finished product.

In the production of crepe yarns, for example, an attempt has been made to prevent the aforesaid barr effect by means of a traversing yarn guide which receives a loop of varying length formed in the yarn extending between the balloon guide of the ring twisting machine and the conveying rollers immediately preceding the balloon guide, when viewed in the direction of yarn travel, the barr effect here being attributed generally to twist fluctuations. This device not only is complicated but also does not obviate the barr effect produced by drawtwisting to any appreciable extent.

It has now been found that the aforesaid barr effect may be substantially reduced, and by the use of a much less complicated process and apparatus. 1

A primary object of this invention, therefore, is to provide a process for drawtwisting yarn formed from linear polycondensation products, especially polyamides, by the use of which the barr effect usually obtained when yarn of this type is woven into fabric will be substantially reduced.

Another object of the present invention is to provide an uncomplicated process for drawtwisting yarn formed from linear polycondensation products by the use of which fabrics woven therefrom will be substantially devoid of any undersirable barr effect.

A further object of this invention is to provide a drawtwisting process by the use of which yarn of improved and more uniform quality will be obtained.

In accordance with the present invention, yarn formed from linear polycondensation products, such as polyamides, is fed from a supply package by the use of feed rollers, is passed over draw pins and led to draw rollers, next is heated and fed to a ring twisting machine having a reciprocating traversing beam, a traveler and a spindle mounted, for rotation about a vertical axis, all of these elements operating in succession on the traveling yarn. The traversing beam has a balloon guide secured thereto for movement therewith. Accordingly, the length of yarn in the balloon, or the length of yarn between the balloon guide and the traveler on the traversing beam, remains constant. Additionally, the heating device is positioned laterally of the normal path of yarn extending between the draw rollers an the ring twisting machine, and therefore serves as an auxiliary guide, whereby yarn may be introduced to the balloon guide at an appreciable angle, preferably on the order of 90, with respect to the axis of rotation of the spindle.

As a result of the fixed relationship between the traversing beam and the balloon guide, which elements determine the actual height of the balloon, said balloon retains substantially the same shape throughout the entire twisting and winding process, without regard to the position of the traversing beam relative to the spindle of the twisting machine. With a constant balloon length, it has been found that tension fluctuations and, consequently, ultimate barr effects will be substantially decreased.

Moreover, it has been observed that a further decrease in barr may be obtained if the yarn is wound with a balloon tension of less than 5 grams per 100 denier. It is understood that the balloon tension as used herein should be measured immediately before the yarn engages the balloon guide of the ring twisting machine. With standard values for the size of the ring, height of the balloon, number of revolutions of the twisting spindle and the yarn supply speed, the aforesaid relatively low balloon tension may best be attained by the use of a lightweight traveler.

A still further improvement in barr effect may be obtained, as mentioned hereinabove, if the yarn is introduced to the balloon guide at an appreciable angle, for

example, an angle approximating with respect to the axis of spindle rotation. If the path of yarn between the balloon guide and the auxiliary guide has a length at least twice that of the yarn in the balloon, or that yarn extending between the balloon guide and the traveler, tension fluctuations normally produced by movement of the traversing beam are, for all practical purposes, substantially eliminated. It can be seen that in conventional drawtwisting machines, having yarn passing substantially vertically downward from the draw rollers to the balloon guide, the supply'speed of yarn with respect to the traveler increases upon ascent of the traversing beam and decreases on descent of this beam. This variation in yarn supply speed produces a variation in the number of revolutions per unit time in the traveler and results in tension variations in the yarn. This disadvantageous condition is obviated if the yarn is introduced or fed to the balloon guide in the manner described hereinabove. It will become apparent that the intensity of tension variations will decrease in proportion to an increase in the angle included between the path of yarn fed to the balloon guide and the axis of the collecting spindle, with the most favorable condition being reached at an angle of 90, or with the yarn being fed to the balloon guide in a path extending normal to the axis of said spindle.

In order to prevent excessive change in the aforesaid angle of yarn introduction during vertical reciprocation of the traversing beam, it is desired that the yarn engaging means immediately preceding the balloon guide be located remote from this guide. As mentioned above, satisfactory results may be obtained if said yarn engaging means is spaced laterally from the balloon guide a distance at least twice that distance between the balloon guide and the traveler. It will be evident, of course, that this yarn engaging means should be positioned or mounted in a horizontal plane coinciding with the balloon guide when the latter element is in a central position with respect to its reciprocating stroke.

The traversing balloon guide feature, and right-angle introduction of yarn thereto, may be used most advantageously, with the most favorable end result insofar as concerns barr effect, if the yarn is heated not only in the drawing stage but also subsequent thereto, with the latter heating occurring under decreased tension. This second heating under decreased tension is particuclariy desirable since most of the yarn shrinkage will occur prior to winding, with only slight shrinkage occurring after the yarn is collected on the twisting spool.

In the event that it is desired to heat the yarn after drawing but before twisting, as described above and as contemplated by the present disclosure, the heating device may be used not only to raise the temperature of the yarn but also as an auxiliary yarn guide functioning to introduce the yarn to the balloon guide at the proper angle in order to obtain minimum tension fluctuations. Thus, the heating means could be used only as a heater, only as an auxiliary yarn guide, or simultaneously as both elements. When used as a heater, this auxiliary yarn guide should be mounted away, or laterally spaced, from the balloon guide a distance of at least three times the length of yarn in the balloon, or three times the length of that yarn extending between the balloon guide and the traveler. It has been found that this additional spacing is necessary if complete shrinking out of the heated yarn is to occur prior to collection on the spindle spool.

Other objects and advantages will become apparent to those skilled in this art upon study of the following detailed description taken in conjunction with the accompanying drawing, which shows a perspective view, in elevation, of a conventional drawtwisting machine modified in accordance with a preferred embodiment of this invention.

With attention now directed to the drawing, reference numeral denotes a yarn brake over which yarn 11 is fed in the direction of the arrow from a supply source (not shown) by feed rollers 12, 13. Roller 12 may be driven by any suitable means (not shown) and roller 13 may be an idler serving only to press the yarn into engagement with driven roller 12, in which case the surface of pressure roller 13 should be formed from an elastic material such as rubber or cork in order to prevent slippage between the yarn and the feed roller. Roller 13 is pivotally supported by a pair of arms 14 (only one of which is identified) and may be urged into engagement with the driven roller 12 by resilient or other means. In any event, rollers 12, 13 serve to feed yarn from the supply source or package to the drawtwisting machine at a substantially constant rate of speed.

A yarn guide 15 serves to increase the contact area between the yarn and pressure roller, which area usually amounts to more than 180, and which additionally deters slippage between the yarn and feed rollers. Yarn guide 15 may be mounted for reciprocation (by means not shown) longitudinally of the pressure roller in order to distribute the wear which usually results from prolonged use. Yarn therefore is fed from a supply source by feed roller 12, 13 while being traversed slowly along the surface of these rollers, all as is known to the art.

The yarn 11 next is directed over a pair of draw pins or bars 16 and then is wound a number of turns about a draw roller 17 and an idler 18. Draw roller 17 is driven (by means not shown) at a peripheral speed substantially greater than the peripheral speed of the feed rollers, which imparts stretch to the traveling yarn. Idler roller 18 is skewed slightly with respect to the axis of draw roller 17 in order to maintain the convolutions of yarn on the draw roller spaced one from the other. The draw pins 16 may be heated, if desired, or maintained at room temperature, depending on the particular yarn receiving treatment.

From the driven roller 17 and idler roller 18, which together constitute the drawing means o drawing rollers, the yarn is fed over a freely rotatable metal roller 2%). Opposite a portion of the circumference thereof, and in such a manner as not to obstruct passage of the yarn thereover, a heating element or device 21 is mounted. The heating element 21, which may receive power electrically as shown in the drawing or by other means, heats the metal idler roller by radiation. It can be seen from this description that roller 20 could serve as a means for heating the yarn, as an auxiliary-guide for describing the yarn path, or as both. As positioned in the drawing, however, roller 20 serves either as an auxiliary guide or as a 16Eltd auxiliary guide.

The yarn is passed from the auxiliary guide roller 20 to balloon guide 22 which defines the upper end of balloon 23. Balloon guide 22 is shown in the drawing as a circumferentially grooved roller, although it is obvious that other means, such as a conventional pig-tail, could be used for this guide as well as for the auxiliary guide. Balloon guide 22 is freely rotatably supported by a rod or supporting arm 24. In the preferred embodiments shown, rod 24 is fixed to a traversing beam 25 of ring twisting machine generally indicated by reference numeral 26. It is obvious that the length of rod 24 could be made adjustable to accommodate the requirements of any particular drawtwisting operation. Moreover, other means could be employed to insure reciprocation of the balloon guide in phase with, and through a stroke equal to, that of the traversing beam. The traversing beam, which may be reciprocated in the direction of the arrows by conventional means (not shown), supports a twisting ring 27 on which is slidably mounted traveler 28. The ring 2 is concentrically disposed about a twisting and collecting spindle 3%) in a manner known and therefore not illustrated in detail. A winding tube or spool 31 is removably secured to the upper portion of spindle 30 by any suitable means known to the art and serves to collect the drawn and twisted yarn fed to the ring twisting machine.

It is thought that the operation of the apparatus described above will be self-evident. Therefore, only that which is necessary to a complete understanding of a specific example will be repeated hereinbelow.

In a practical embodiment of the present invention, an undrawn polycaprolactam yarn having 36 filaments and a titre of 32.2 tex (approximately 290 denier) was drawn between feed rollers 12, 13 and draw rollers 17, 18 of the apparatus described hereinabove until the yarn was 3.12 times its original length. The drawn yarn was fed from the drawn rollers at a speed of 360 meters per minute and was heated on heated auxiliary roller 20 to a temperature of 113 C.

After being heated on roller 20, the yarn passed through an air path or Zone of cm. leading to the balloon guide roller 22, after which it was directed to the traveler 28 of ring twisting machine 26, twisted and collected on winding tube 31.

The balloon guide 22 was set at a height of 25 cm. above the traversing beam 25. The length of yarn in the balloon 23, or the actual length of yarn extending between the guide 22 and traveler 28, however, was slightly greater and approximated 30 cm. The traveler 23 had a weight of 38 mg. and the diameter of the twisting ring 2'7 was 8.7 cm. The spindle 30 was rotated at 7900 revolutions per minute. As a result of the foregoing values, yarn was wound on the winding tube 31 with a balloon tension of 4.8 grams per 100 denier and was shrunk in the cooling zone extending between auxiliary guide 20 and balloon guide 22 about 2.3 percent.

The yarn obtained from the example discussed above had an elongation of 42 percent with a strength of 480 grams per 11.1 tex (approximately 480 grams per denier). This yarn was transferred directly from winding tube 31 to spools and then woven into fabric. The fabric thus obtained showed, for all practical purposes, no barr effect.

In performing the invention in the manner described above, the balloon guide preferably is traversed along the axis of or in alignment with the twisting spindle. It has been found, however, that substantially the sme decrease in barr effect may be obtained if this guide is reciprocated along a path somewhat inclined with respect to the spindle axis.

Moreover, it is obvious that yarns having other deniers, and even monofilament yarn, may be processed according to the present invention. Other draw ratios and other heating temperatures, as well as cooling zones of different lengths, also may be utilized.

It is intended that linear polycondensation products as used herein include not only polyamides produced from lactams or from dicarboxylic acids and diamines, but also polyesters and polyurethanes. When applying this invention to yarns consisting of polymers other than polyamides, the heating temperature of course must be adjusted with respect to the melting point of the particular polymer used. The correct temperature may be determined easily by experiment.

Under some circumstances, it may be desirable to unwind the yarn from winding tube 31 immediately or soon after the twisting operation. In the event that complete shrinkage does not occur during twisting and winding, the decreased barr effect can best be obtained by rewinding the yarn on a package which allows continued unopposed shrinkage.

When heating under a condition of decreased tension as proposed hereinabove, however, immediate rewinding is not usually necessary, especially if the yarn is guided through an extended cooling zone after heating but prior to twisting and collecting. This extended cooling zone should be of a length at least three times the length of yarn in the balloon, as mentioned earlier. In a cooling zone of such an extended length, the yarn is permitted to shrink sufliciently so that after-shrinking on the winding tube, if occurring at all, is not of serious consequence. The minimum length requirement for the cooling zone is applicable to the usual draw speeds of about 360 meters per minute, calculated on the drawn yarn. If higher drawing speeds are used, a cooling zone of greater length must be provided.

The foregoing detailed description of one specific embodiment of this invention is intended for purposes of illustration only and is not to be construed as limiting the scope of the following claims.

What is claimed is:

1. A process for treating drawn yarn formed from polycondensation products to reduce pirn barr comprising the steps of feeding said drawn yarn into a rotating balloon from a direction approximately at right angles to the axis of balloon rotation, said yarn being unsup ported prior to entry into said balloon for a distance at least twice the length of ballooning yarn, collecting said ballooning yarn in package form while imparting twist thereto, and maintaining the length of yarn in said balloon constant during collection without substantial variation in yarn tension throughout the process.

2. A process for treating drawn yarn formed from polycondensation products to reduce pirn barr comprising the steps of raising the temperature of said drawn yarn by heating the same, feeding said drawn and heated yarn into a rotating balloon from a direction approximately at right angles to the axis of balloon rotation, said yarn being unsupported prior to entry into said balloon for a distance at least three times the length of ballooning yarn, collecting said ballooning yarn in package form while imparting twist thereto, and maintaining the length of yarn in said balloon constant during collection without substantial variation in yarn tension throughout the process.

References Cited in the file of this patent UNITED STATES PATENTS 959,198 Boyd May 24, 1910 1,793,704 Lenk Feb. 24, 1931 2,160,010 Whittemore May 30, 1939 2,256,150 Mallory Sept. 16, 1941 2,336,100 .T'acque Dec. 7, 1943 2,432,564 Elvin et a1. Dec. 16, 1947 2,464,536 Solliday et a1 Mar. 15, 1949 2,509,741 Miles May 30, 1950 2,728,973 Kummel Jan. 3, 1956 2,803,108 Stoddard et al Aug. 20, 1957 2,854,814 Burkholder Oct. 7, 1958 

